Technical Field
The present disclosure relates to high-frequency amplifier circuits that amplify and then output an input high-frequency signal.
Background Art
A variety of high-frequency amplifier circuits are used in wireless communication terminals. Among such high-frequency amplifier circuits, there are high-frequency amplifier circuits configured to be able to change among a plurality of operation modes. For example, a high-frequency amplifier circuit as described in Patent Document 1 is used. FIG. 17 is a circuit diagram of a typical high-frequency amplifier circuit as described in Patent Document 1.
A high-frequency amplifier circuit 10P of the related art includes an amplifier 101 composed of an npn transistor and a bias determiner 20P. An emitter of the amplifier 101 is grounded. A base of the amplifier 101 is connected via an input matching circuit 901 to an RF input terminal Pin through which a high-frequency signal is input. A collector of the amplifier 101 is connected via an output matching circuit 902 to an RF output terminal Pout through which an amplified high-frequency signal is output.
The collector of the amplifier 101 is connected to a driving voltage application terminal PVCC via a coil 301 and a direct-current driving voltage VCC is applied to the collector of the amplifier 101 from the driving voltage application terminal PVCC. A connection point between the driving voltage application terminal PVCC and the coil 301 is grounded by a capacitor 401.
The bias determiner 20P includes a bias control element 102 composed of an npn transistor. An emitter of the bias control element 102 is connected via a resistor 201 to the base of the amplifier 101 used for high-frequency amplification. A bias driving voltage application terminal PVC0 is connected to a collector of the bias control element 102 and a direct-current bias driving voltage VC0 is applied to the collector of the bias control element 102 from the bias driving voltage application terminal PVC0.
A control voltage input terminal PVCTL is connected via a resistor 202 to a base of the bias control element 102 and a direct-current control voltage VCTL is applied to the base of the bias control element 102 from the control voltage input terminal PVCTL.
In this high-frequency amplifier circuit 10P of the related art, a control voltage VCTL corresponding to an operation mode is applied to the base of the bias control element 102. In a low linearity mode, the control voltage VCTL is made low. As a result, a base current IBB supplied to the amplifier 101 used for high-frequency amplification from the bias control element 102 becomes low, the level of an output high-frequency signal can be lowered and power consumption can be suppressed. In a high linearity mode, the control voltage VCTL is made high. As a result, the base current IBB supplied to the amplifier 101 used for high-frequency amplification from the bias control element 102 can be made high and the level of an output high-frequency signal can be made high.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 11-330866